Construction adhesive behind stainless steel backsplash a must???

Hi, tomorrow a helper is coming to help me install a 36"x30" stainless steel backsplash. We need to take the exhaust fan off because the backsplash is higher than the available gap above countertop, and the sheet is too ridge to be forced in in the gap behind. The edges in the sheet are bent back in and there are four holes in the corners for fasteners.
Here is my question: if we are screwing the four corners, why does the instruction say construction adhesive is also required? Having installed many things, I've learned that if you can avoid making things permanent, do avoid it -- you never know when you may need to take something off. For that reason, I'm hesitant about applying the adhesive. Can someone tell me what might happen if I don't apply the adhesive (after the four corners are screwed against the wall)?

Oh, BTW, after installing the backsplash, we are going to tile on both sides and caulk the gaps. In the long run, if something bad happened because I skipped the adhesive, it will not be that easy to redo it because it will again involve redoing the exhaust fan and caulking with the tiles on both sides. So, I want to do it right, but still want to avoid gluing it down if its not necessary. Hence my question...

Use silicon or polymer caulk that does not dry out. If needed to remove, you can slip a knife or razor behind the panel to cut. Apply the glue with fine tooth trowel (you can get a disposable) and apply evenly all over the panel. Beaded glue may show up in the front.
You will have to drill or cut a hole for the electric line. Make sure the cut edge is smooth, at least.

Thanks again all for the replies. Things did not work out as planned, but maybe it's for the better. The helper showed up late, so I tried to look at the task myself. Decided to cut the caulking out between the wall and the countertop behind the cooktop. It allowed me to insert the backsplash downward enough for me to muscle the entire backsplash in place from under the hood. I preemptively shaved some drywall off where the gap is smaller than the thickness. Glad that I did because although I did it with the intention of trying out/dry fitting, I ended up having a hell of a time to back it out. Actually, it was so hard that I gave up. So, I simply brought the top forward to give me enough room to squeeze some adhesive in. Due to the awkward access, I just did snake pattern. BTW, the bottom two screw holes are behind the countertop and not accessible. The top two screw holes are so close to the hood and cabinets that I simply cannot go straight in. And when I tried, they were not hitting studs anyway, and I can't get the drywall anchor in. So, I'm mostly relying on the adhesive now to hold the backsplash. That's it. No removal in the future!

When the helper finally arrived, he was surprised to see that I already finished installing the backsplash.